Acres to Square Miles
Convert acres (ac) to square miles (mi²). Both measure surface measurement, and the conversion comes up in real estate, farming, construction work.
The Formula
``
square miles = acres × 0.0015625
acres = square miles × 640
`
One acre is 0.001563 square miles, and one square mile is 640 acres.
Conversion Table
| Acres | Square Miles |
|---|---|
| 1 ac | 0.001563 mi² |
| 2 ac | 0.003125 mi² |
| 5 ac | 0.007813 mi² |
| 10 ac | 0.015625 mi² |
| 25 ac | 0.039063 mi² |
| 50 ac | 0.078125 mi² |
| 100 ac | 0.15625 mi² |
| 500 ac | 0.78125 mi² |
| 1,000 ac | 1.5625 mi² |
The Other Direction
| Square Miles | Acres |
|---|---|
| 1 mi² | 640 ac |
| 2 mi² | 1,280 ac |
| 5 mi² | 3,200 ac |
| 10 mi² | 6,400 ac |
| 25 mi² | 16,000 ac |
| 50 mi² | 32,000 ac |
| 100 mi² | 64,000 ac |
| 500 mi² | 320,000 ac |
| 1,000 mi² | 640,000 ac |
What Each Unit Is
Acres (ac) — exactly 4,046.8564224 square metres, or one furlong by one chain. The area a yoke of oxen could plough in a day — long and thin, because turning wasted time.
Square Miles (mi²) — 640 acres, or 2.589988 square kilometres. The unit of the US Public Land Survey System, which divided the west into square-mile sections.
A Sense of Scale
An American football field is 1.32 acres- A soccer pitch is about 1.8 acres
- A survey township is 36 square miles
- San Francisco is 47 square miles
Precision
The factor 0.0015625 is exact by international agreement, not a rounded approximation. Any imprecision in a result comes from your input, not the conversion.
In Code
`javascript
const acreToSquareMile = (value) => value * 0.0015625;
``
Where This Conversion Comes Up
- Real estate
- Farming
- Construction
- Landscaping
- Flooring
How Many Decimals Do You Need?
Rounding the factor costs accuracy, and how much depends on the factor. Converting 137 ac with the factor truncated at each decimal place:
| Decimals kept | Factor | 137 ac becomes | Error |
|---|---|---|---|
| 0 | 0 | 0 | 100.0000% |
| 1 | 0 | 0 | 100.0000% |
| 2 | 0 | 0 | 100.0000% |
| 3 | 0.002 | 0.274 | 28.0000% |
| 4 | 0.0016 | 0.2192 | 2.4000% |
The right number of significant figures is set by your input, not by the converter. If you measured acres to three significant figures, the answer in square miles is only good to three — writing more digits claims precision the measurement never had.